This invention relates to a fuel delivery rail assembly for an internal combustion engine, especially for an automotive engine, equipped with a fuel injection system The fuel delivery rail assembly delivers pressurized fuel supplied from a fuel pump toward intake passages or chambers via associated fuel injectors. The assembly is used to simplify installation of the fuel injectors and the fuel supply passages on the engine.
An ordinary fuel delivery rail assembly having a rectangular section is constructed as shown in FIG. 5 of the drawings. In this assembly, an elongated conduit 61 is formed by a steel tube having a rectangular hollow section. To an end of the conduit 61, a fuel inlet pipe 67 for introducing gasoline fuel is secured, and to the other end of the conduit 61, a fuel return pipe 68 leading to an exit for residual fuel is secured, both pipes being welded to the conduit by copper brazing. To the inside of the conduit 61 and the pipes 67, 68, copper plating or nickel plating is coated for protecting the surfaces from rust and for keeping the fuel clean.
The conduit 61 comprises four walls and a fuel passage therein. To an outside surface of one wall, are attached a plurality of sockets 64, the number of which corresponds to the number of combustion cylinders. One end of each socket 64 communicates with the fuel passage, and the other end of each socket 64 is so formed as to receive an associated tip of a fuel injector In most cases, these sockets 64 are inserted into guide holes arranged within the wall of the conduit 61 at predetermined intervals, and welded thereto by copper brazing. The axial directions of the sockets 64 should precisely line up in alignment with the respective axial direction of the injectors. Furthermore, pitch lengths between adjacent sockets should precisely coincide with the corresponding pitch lengths between associated injectors. One of the objects of the present invention is directed to connecting problems between the conduit and the sockets.
In Japanese utility model public disclosure No. 84362/1982, two types of fuel delivery rail assembly are disclosed. One is a projection welding type in which the sockets and the conduit are connected by the projection welding, and the other is a die casting type in which the sockets and the conduit are integrally formed through a die casting process.
While welding type connections between the sockets and the conduit have met with some amount of technical success, they have not been as successful as might have been expected given that there have been several manufacturing problems due to a heat distortion. For the purpose of eliminating fuel leakage from the connections due to the heat distortion, it is necessary to carefully examine every assembly. If a defective connection is found, the assembly should be thrown away, resulting in an increase of manufacturing cost.
Furthermore, a surface treatment should be applied to the assembly after the welding process. Since the surface adjacent the socket is irregularly finished, it is difficult to maintain high quality of the surface treatment.
As an alternative construction, an integral type of die casted fuel delivery rail assembly is disclosed in the aforementioned public disclosure. However, it has been found that this kind of integral type cannot be prepared for complicated forms corresponding to miscellaneous engines.
In Japanese utility model public disclosure No. 144068/1983, there is disclosed an integral type of fuel delivery rail assembly in which plastic sockets are molded integral with a plastic conduit through an injection molding process. However, it has been found that it is considerably difficult to make a mold and a block insert for the molding process. Moreover, since the assembly has poor rigidity, it is easily bent thereby causing a fuel leakage or breakdown, which leads to a danger of fire.